An investigation on flexural properties of anti-tetrachiral auxetic structures fabricated by material extrusion

Abstract

The present paper describes an investigation on flexural properties of anti-tetrachiral auxetic structures fabricated by material extrusion technique of additive manufacturing. Flexural performance of these structures is crucial in automotive crash box, robust shock absorbers, air seat cushions, sound absorbers, air filters, airfoil morphing, biomedical stent, non-pneumatic tyres, vibration attenuation, and impact detection sensors. Mechanical properties of auxetic structure depend on geometric parameters of its unit cell. Therefore, in the present study, influence of two geometric parameters namely cylinder radius and ligament thickness on modulus, strength and specific energy absorption (SEA) of in-plane and out-of-plane oriented structures under flexural loading has been investigated. Experimental plan is prepared using central composite design method of response surface methodology. Specimens of acrylonitrile butadiene styrene (ABS) material are fabricated using material extrusion technique. Each specimen is tested under three-point flexural loading as per ASTM D790. Experimental results are analysed using analysis of variance (ANOVA). It is found that both geometric parameters influence modulus, strength and SEA of in-plane and out-of-plane oriented structure significantly. For both orientations of structure, modulus and strength increase with decrease in cylinder radius and increase in ligament thickness, while SEA increases with increase in cylinder radius and decrease in ligament thickness. Further, optimization of geometric parameters is performed using grey relational analysis to maximize the responses. Regression models are also developed to predict the responses. The findings of present study are useful in maximizing flexural properties of anti-tetrachiral auxetic structures through selection of optimum geometric parameters of unit cell.